Method for etching nickel



Patented Mar. 4, 1941 UNITED STATES PATENT OFFICE No Drawing. Application May 24, 1939, Serial No. 275,514

Claims.

This invention relates to the etching of metallic nickel and is of special interest to the arts of metal-decoration and photo-mechanical printing. A primary object of the invention is to 5 secure a medium for the rapid and smooth etching of a nickel layer supporting colloid reliefs as local resists. Other objects of the invention are to secure an equal or nearly equal rate for the etching of nickel and copper, and to secure etching solutions which will etch nickel and cdpper at con-trolled differential rates.

Reference is made to the copending patent application of C. E. Meulendyke (Ser. No. 277,843). In this invention a photo-mechanical or halftone printing plate is prepared by coating a silver halide emulsion layer upon a metallic sheet such as a copper base electroplated with a nickel layer and having a layer of lacquer or varnish interposed between the nickel layer and the emulsion layer. After exposing and processing the emulsion layer .to a relief and forming a secondary resist out of the lacquer or varnish layer the metallic plate is then etched. If, as will be appreciated by those skilled in the art, it is de- 25 sired to etch through the nickel layer into the copper base, a further problem arises of etching the nickel and the copper at an equal or nearly equal rate to avoid undercutting of the nickel at the interface of the two metals.

As is well-known in the art of photo-mechanical printing, a solution of ferric chloride is generally used to etch copper. I have found that cupric chloride solutions will etch nickel smoothly and rapidly in either water or alcoholic solutions. 35 I have further found that while solutions of ferric chloride will etch copper more rapidly than nickel that solutions of cupric chloride either alone or in suitable conjunction with ferric chloride, will etch through a nickel layer into a 40 copper base without undercutting of the nickel. Brush-etching appears .to be a favorable method with these solutions. Solutions of ferric chloride alone will etch copper approximately two and one-half times faster than they will etch nickel. On the other hand I have found that solutions of cupric chloride alone will etch nickel approximately twice as fast as solutions of ferric chloride. I have further found that an alcoholic solution of cupric chloride will etch nickel rapidly but has no appreciable etching action upon copper. I have also found that in etching through an electroplated nickel layer into a copper base with the nickel layer supporting a half-tone resist, undercutting of the nickel layer can be avoided by etching in suitable solutions containing both ferric chloride and cupric chloride; that half-tone plates produced in this manner will yield suitable lead molds for making electrotypes and suitable mats for making stereotypes. I have further found in etching through an electro- 5 plated nickel layer into a copper base with the nickel layer supporting a half-tone or line resist that after the nickel has been cut through a second stage etching solution containing a suitable mixture of ferric chloride and cupric chloride can control the slope of the depressions permitting great depth of etching without powdering and protecting the sides of such depressions. It is also possible .to etch through the nickel layer into the copper using straight ferric chloride as 16 etchant, actually forming undercut nickel and-then correcting such undercutting in a second etching solution of straight cupric chloride or of a. suitable mixture of cupric chloride and ferric chloride. 20

I believe I am the first to suggest the use of cupric chloride solutions for the etching of nickel.

I believe I am the first to suggest solutions of cupric chloride either alone or in conjunction with ferric chloride to etch through a nickel layer into a copper base to avoid undercutting of the nickel layer. As suitable solutions for etching nickel where cupric chloride alone is used I suggest a water or alcoholic solution containing 40% by weight of cupric chloride. After etching through a nickel layer into a copper base, I suggest the use of a solution containing twothirds of ferric chloride and one-third of cupric chloride to correct and prevent undercutting of the nickel layer and to control the slope of the 3:; sides of the depressions.

Within the meaning of this invention I intend to include the etching of suitable nickel alloys as well as the etching of a pure nickel layer. Also, I intend that any suitable metallic base 40 shall be used including zinc, iron, aluminum, copper, and their alloys. Also, I intend to include cupric chloride used alone or in conjunction with other suitable materials to form an etching medium. Also I intend to include cupric chloride added as such to an etching solution or which may arise from the dissolution of metallic copper in an etching operation.

It will thus be seen that I have described processes with all necessary details embodying the principles and attaining the objects and advantages of the invention. Since many matters of treatment, manipulation, selection and proportion of ingredients, succession of steps, and other details may be variously modified without 5 2. m the arts of metal-decoration and photo-,

mechanical printing, the method of etching into a metallic base through a metallic nickel layer plated thereon and supporting suitable local resists including the use of a solution including cupric chloride.

3. In the arts of metal-decoration and photomechanical printing, the method of etching into a metallic base through a metallic nickel layer plated thereon and supporting suitable local resists including the steps of etching through the nickel layer .with-anysuitable etching medium and then etching the exposed nickel edges and base metal surfaces in an etching solution including cupric chloride.

4. In the arts of metal-decoration and photomechanical printing, the method of etching into a copper base through a metallic nickel layer plated thereon and supporting suitable local resists including the steps of etching through the nickel layer. with any suitable etchin .medium and then etchingthe exposed nickel edges and copper surfaces in'an etching solution including 1 cupric chloride.

5. In the arts of metal-decoration and photomechanical printing, the method of etching into a copper base through a metallic nickel layer plated thereon and supporting suitable local re- 15 sists including the steps of etching through the nickel layer with any suitable etching medium and then etching the exposed nickel edges and copper surfaces in an etching solution including cupric chloride'and ferric chloride.

CHARLES EDMUND I 

